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The present invention relates to speed control of an optical information reproducing apparatus, and more in particular, to speed control of the optical information reproducing apparatus based on storage quantity of a buffer memory therein during access operation.
The optical information reproducing apparatus, such as CD-ROM, DVD-ROM, CD-RW or DVD-RAM, has been a basic component of a multi-media computer system.
The U.S. Pat. Nos. 4,485,337, 4,783,774, 5289,097, 5246,479, and 5,345,347 disclose prior arts of control system relating to the optical information reproducing apparatus.
Nowadays, the nominal operation speed of commercial optical information reproducing apparatus is represented by multiples of a basic unit, X. It is well known that 1X is equal to 176 kilobytes per second for CD-ROM standard. The key component affecting the nominal operation speed of the optical information reproducing apparatus is the rotation rate of spindle motor inside the optical information reproducing apparatus. In general, at the commencement of read operation of optical information reproducing apparatus, the optical information reproducing apparatus is set at a predetermined maximum speed. As lower read rate occurs due to various conditions, e.g., out-of-focus, eccentric or vibration of optical disc, the optical information reproducing apparatus will automatically lower its operation speed to achieve a correct rate. In addition, for some optical discs having specific data format, the optical information reproducing apparatus sets a read rate specifically corresponding to the data format of disc to achieve a preferred read rate. The well known data format types include CD-Audio disclosed by Red Book, CD-ROM Model, CD-ROM Mode2 disclosed by Yellow Book, CD-ROM Mode2/XA Forml, CD-ROM Mode2/XA Form2 disclosed by Green Book, Recordable Compact Disc Standard disclosed by Orange Book, etc. The types of disc data formats readable to an optical information reproducing apparatus are stored within the firmware of the optical information reproducing apparatus. As the optical disc with an extended data format, such as MP3 format or PC-Game format read by the optical information reproducing apparatus, is not one of the well known data format types, the optical information reproducing apparatus treats the extended data format as a general data format type and reads the optical disc by allowable maximum speed. Under this condition, usually a software or hardware decoding approach is required in the optical information reproducing apparatus to determine and set the operating speed of optical information reproducing apparatus. However, this approach is expensive and difficult to implement.
The current design for the optical information reproducing apparatus gravitates towards higher operation thereof. However, noise due to wind-cutting, vibration and motor humming usually accompanies higher operation speed of the optical information reproducing apparatus. The noise is specifically significant with respect to disc of non-standard data format running at allowable maximum speed. The noise combined with the eccentric defect associated with the optical disc may seriously jeopardize the reproduction of data, i.e., audio and video effect, of the disc.
In addition, as the data read rate of data required when an application requires a data reading rate far less than that provided by the optical information reproducing apparatus, the optical information reproducing apparatus will still be operated at higher speed, to consume unnecessary power and shorten the lifetime of spindle motor.
The foregoing and other state-of-the-art control systems for optical information reproducing apparatus indicate the need for a new method of automatically tuning the rotation rate of spindle motor at a suitable rate to eliminate noise and yet without affecting information reproducing efficiency of the optical information reproducing apparatus. It is also desired to obtain a control system for driving an optical information reproducing apparatus with a relatively low power consumption and a high power conversion efficiency. The present invention is directed toward satisfying the aforesaid need.
One objective of the invention is to provide a method which automatically tunes the speed of the spindle motor at a suitable rate to eliminate noise and lower power consumption without affecting information reproducing efficiency.
In the invention, the optical information reproducing apparatus has a buffer memory for temporarily storing data read from the optical disc. The method of the invention is to decelerate or accelerate the spindle motor by monitoring the storage quantity of the buffer memory during operation.
According to a first preferred embodiment of the invention, a method for controlling rotation rate of the spindle motor determines if the storage quantity of the buffer memory is successively larger than a first predetermined quantity during a period of read operation, and, if so, the spindle motor is decelerated with a predetermined variation rate. The method also determines whether the storage quantity of the buffer memory is successively less than a second predetermined quantity during a period of read operation, and, if so, the spindle motor is accelerated with the predetermined variation rate.
According to a second preferred embodiment of the invention, a method for controlling speed of the spindle motor determines if the storage quantity of the buffer memory is successively larger than a first predetermined quantity during a period of read operation, and determines if a waiting time is longer than a predetermined time. If so, the spindle motor is decelerated with a predetermined variation rate. The waiting time represents the time consumed in waiting for an instruction asserted by the application program, which requests data transfer. The method also determines if the storage quantity of the buffer memory is successively less than a second predetermined quantity during a period of read operation, and, if so, the spindle motor is accelerated with the predetermined variation rate.